Planetary transmissions having four interconnecting members and clutched input members

ABSTRACT

The family of transmissions has a plurality of members that can be utilized in powertrains to provide at least eight forward speed ratios and one reverse speed ratio. The transmission family members include three planetary gear sets having seven torque-transmitting mechanisms and four interconnecting members. The powertrain includes an engine that is selectively connectable to at least one of the planetary gear members and an output member that is continuously connected with another one of the planetary gear members. The seven torque-transmitting mechanisms provide interconnections between various gear members, the input shaft and the transmission housing, and are operated in combinations of two to establish at least eight forward speed ratios and at least one reverse speed ratio.

TECHNICAL FIELD

The present invention relates to a family of power transmissions havingthree planetary gear sets that are controlled by seventorque-transmitting devices to provide at least eight forward speedratios and at least one reverse speed ratio.

BACKGROUND OF THE INVENTION

Passenger vehicles include a powertrain that is comprised of an engine,multi-speed transmission, and a differential or final drive. Themulti-speed transmission increases the overall operating range of thevehicle by permitting the engine to operate through its torque range anumber of times. The number of forward speed ratios that are availablein the transmission determines the number of times the engine torquerange is repeated. Early automatic transmissions had two speed ranges.This severely limited the overall speed range of the vehicle andtherefore required a relatively large engine that could produce a widespeed and torque range. This resulted in the engine operating at aspecific fuel consumption point during cruising, other than the mostefficient point. Therefore, manually-shifted (countershafttransmissions) were the most popular.

With the advent of three- and four-speed automatic transmissions, theautomatic shifting (planetary gear) transmission increased in popularitywith the motoring public. These transmissions improved the operatingperformance and fuel economy of the vehicle. The increased number ofspeed ratios reduces, the step size between ratios and thereforeimproves the shift quality of the transmission by making the ratiointerchanges substantially imperceptible to the operator under normalvehicle acceleration.

It has been suggested that the number of forward speed ratios beincreased to six or more. Six-speed transmissions are disclosed in U.S.Pat. No. 4,070,927 issued to Polak on Jan. 31, 1978; and U.S. Pat. No.6,422,969 issued to Raghavan and Usoro on Jul. 23, 2002.

Six-speed transmissions offer several advantages over four- andfive-speed transmissions, including improved vehicle acceleration andimproved fuel economy. While many trucks employ power transmissionshaving six or more forward speed ratios, passenger cars are stillmanufactured with three- and four-speed automatic transmissions andrelatively few five or six-speed devices due to the size and complexityof these transmissions.

Seven-speed transmissions are disclosed in U.S. Pat. No. 6,623,397issued to Raghavan, Bucknor and Usoro. Eight speed transmissions aredisclosed in U.S. Pat. No. 6,425,841 issued to Haka. The Hakatransmission utilizes three planetary gear sets and six torquetransmitting devices, including two brakes and two clutches, to provideeight forward speed ratios and a reverse speed ratio. One of theplanetary gear sets is positioned and operated to establish two fixedspeed input members for the remaining two planetary gear sets. Seven-,eight- and nine-speed transmissions provide further improvements inacceleration and fuel economy over six-speed transmissions. However,like the six-speed transmissions discussed above, the development ofseven-, eight- and nine-speed transmissions has been precluded becauseof complexity, size and cost.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved familyof transmissions having three planetary gear sets controlled to provideat least eight forward speed ratios and at least one reverse speedratio.

In one aspect of the present invention, the family of transmissions hasthree planetary gear sets, each of which includes a first, second andthird member, which members may comprise a sun gear, a ring gear, or aplanet carrier assembly member, in any order.

In referring to the first, second and third gear sets in thisdescription and in the claims, these sets may be counted “first” to“third” in any order in the drawings (i.e., left to right, right toleft, etc.).

In another aspect of the present invention, the planetary gear sets maybe of the single pinion-type or of the double pinion-type.

In yet another aspect of the present invention, a first member of thefirst planetary gear set is continuously interconnected with a firstmember of the second planetary gear set through a first interconnectingmember.

In yet another aspect of the present invention, a second member of thefirst planetary gear set is continuously interconnected with a secondmember of the second planetary gear set through a second interconnectingmember.

In yet another aspect of the present invention, a third member of thefirst planetary gear set is continuously interconnected with a firstmember of the third planetary gear set through a third interconnectingmember.

In yet another aspect of the present invention, a third member of thesecond planetary gear set is continuously interconnected with a secondmember of the third planetary gear set through a fourth interconnectingmember.

The interconnecting members may be multi-piece rigid connections, singlepiece rigid connections, shared ring gears, shared carriers, shared sungears, long pinions, such as in a Ravigneax gear set, or other suitabledevices.

In yet a further aspect of the invention, each family memberincorporates an output shaft which is continuously connected with atleast one member of the planetary gear sets, and an input shaft which isnot continuously connected with any member of the planetary gear setsbut is selectively connectable with at least one member of the planetarygear sets through at least one of seven torque-transmitting mechanisms(torque transfer devices).

In still a further aspect of the invention, a first torque-transmittingmechanism, such as a clutch, selectively interconnects a member of thefirst planetary gear set with the input shaft.

In another aspect of the invention, a second torque-transmittingmechanism, such as a clutch, selectively interconnects a member of thesecond planetary gear set with the input shaft.

In a still further aspect of the invention, a third torque-transmittingmechanism, such as a clutch, selectively interconnects a member of thefirst or third planetary gear set with the input shaft.

In a still further aspect of the invention, a fourth torque-transmittingmechanism, such as a brake, selectively interconnects a member of thefirst planetary gear set with a stationary member (ground/transmissioncase).

In a still further aspect of the invention, a fifth torque-transmittingmechanism, such as a brake, selectively connects a member of the secondplanetary gear set with the stationary member (ground/transmissioncase).

In still another aspect of the invention, a sixth torque-transmittingmechanism, such as a brake, selectively connects a member of the firstor third planetary gear set with the stationary member(ground/transmission case).

In still another aspect of the invention, a seventh torque-transmittingmechanism, such as a clutch, selectively interconnects a member of thefirst, second or third planetary gear set with another member of thefirst, second or third planetary gear set. Alternatively, the seventhtorque-transmitting mechanism, such as a brake, selectively connects amember of the first, second or third planetary gear set with thestationary member (ground/transmission case).

In still another aspect of the invention, the seven torque-transmittingmechanisms are selectively engageable in combinations of two to yield atleast eight forward speed ratios and at least one reverse speed ratio.

The above objects and other objects, features, and advantages of thepresent invention are readily apparent from the following detaileddescription of the best modes for carrying out the invention when takenin connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a schematic representation of a powertrain including aplanetary transmission incorporating a family member of the presentinvention;

FIG. 1 b is a truth table and chart depicting some of the operatingcharacteristics of the powertrain shown in FIG. 1 a;

FIG. 2 a is a schematic representation of a powertrain having aplanetary transmission incorporating another family member of thepresent invention;

FIG. 2 b is a truth table and chart depicting some of the operatingcharacteristics of the powertrain shown in FIG. 2 a;

FIG. 3 a is a schematic representation of a powertrain having aplanetary transmission incorporating another family member of thepresent invention;

FIG. 3 b is a truth table and chart depicting some of the operatingcharacteristics of the powertrain shown in FIG. 3 a;

FIG. 4 a is a schematic representation of a powertrain having aplanetary transmission incorporating another family member of thepresent invention;

FIG. 4 b is a truth table and chart depicting some of the operatingcharacteristics of the powertrain shown in FIG. 4 a;

FIG. 5 a is a schematic representation of a powertrain having aplanetary transmission incorporating another family member of thepresent invention;

FIG. 5 b is a truth table and chart depicting some of the operatingcharacteristics of the powertrain shown in FIG. 5 a;

FIG. 6 a is a schematic representation of a powertrain having aplanetary transmission incorporating another family member of thepresent invention;

FIG. 6 b is a truth table and chart depicting some of the operatingcharacteristics of the powertrain shown in FIG. 6 a;

FIG. 7 a is a schematic representation of a powertrain having aplanetary transmission incorporating another family member of thepresent invention; and

FIG. 7 b is a truth table and chart depicting some of the operatingcharacteristics of the powertrain shown in FIG. 7 a.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, wherein like characters represent the same orcorresponding parts throughout the several views, there is shown in FIG.1 a a powertrain 10 having a conventional engine 12, a planetarytransmission 14, and a conventional final drive mechanism 16.

The planetary transmission 14 includes an input shaft 17 connected withthe engine 12, a planetary gear arrangement 18, and an output shaft 19continuously connected with the final drive mechanism 16. The planetarygear arrangement 18 includes three planetary gear sets 20, 30 and 40.

The planetary gear set 20 includes a sun gear member 22, a ring gearmember 24, and a planet carrier assembly 26. The planet carrier assembly26 includes a plurality of pinion gears 27 rotatably mounted on acarrier member 29 and disposed in meshing relationship with both the sungear member 22 and the ring gear member 24.

The planetary gear set 30 includes a sun gear member 32, a ring gearmember 34, and a planet carrier assembly member 36. The planet carrierassembly member 36 includes a plurality of pinion gears 37 rotatablymounted on a carrier member 39 and disposed in meshing relationship withboth the sun gear member 32 and the ring gear member 34.

The planetary gear set 40 includes a sun gear member 42, a ring gearmember 44, and a planet carrier assembly member 46. The planet carrierassembly member 46 includes a plurality of pinion gears 47 rotatablymounted on a carrier member 49 and disposed in meshing relationship withboth the sun gear member 42 and the ring gear member 44.

The planetary gear arrangement also includes seven torque-transmittingmechanisms 50, 52, 54, 56, 57, 58 and 59. The torque-transmittingmechanisms 50, 52, 54 and 56 are rotating-type torque-transmittingmechanisms, commonly termed clutches. The torque-transmitting mechanisms57, 58 and 59 are stationary-type torque transmitting mechanisms,commonly termed brakes or reaction clutches.

The input shaft 17 is not continuously connected with any planetary gearmember. The output shaft 19 is continuously connected with the ring gearmember 44. The carrier 26 is continuously connected with the planetcarrier assembly member 36 through the interconnecting member 72. Thering gear member 24 is continuously connected with the sun gear member32 through the interconnecting member 72. The sun gear member 22 iscontinuously connected with the sun gear member 42 through theinterconnecting member 74. The ring gear member 34 is continuouslyconnected with the planet carrier assembly member 46 through theinterconnecting member 76.

The ring gear member 24 is selectively connectable with the input shaft17 through the clutch 50. The planet carrier assembly member 26 isselectively connectable with the input shaft 17 through the clutch 52.The sun gear member 22 is selectively connectable with the input shaft17 through the clutch 54. The planet carrier assembly member 46 isselectively connectable with the input shaft 17 through the clutch 56.The ring gear member 24 is selectively connectable with the transmissionhousing 60 through the brake 57. The planet carrier assembly member 36is selectively connectable with the transmission housing 60 through thebrake 58. The ring gear member 34 is selectively connectable with thetransmission housing through the brake 59.

As shown in FIG. 1 b, and in particular the truth table disclosedtherein, the torque-transmitting mechanisms are selectively engaged incombinations of two to provide eight forward speed ratios and tworeverse speed ratios.

The reverse speed ratio is established with the engagement of the clutch50 and brake 58. The clutch 50 connects the ring gear member 24 with theinput shaft 17. The brake 58 connects the planet carrier assembly member36 with the transmission housing 60. The ring gear member 24 and sungear member 32 rotate at the same speed as the input shaft 17. Theplanet carrier assembly members 26 and 36 do not rotate. The sun gearmember 22 rotates at the same speed as the sun gear member 42. The speedof the sun gear member 22 is determined from the speed of the ring gearmember 24 and the ring gear/sun gear tooth ratio of the planetary gearset 20. The ring gear member 34 rotates at the same speed as the planetcarrier assembly member 46. The speed of the ring gear member 34 isdetermined from the speed of the sun gear member 32 and the ringgear/sun gear tooth ratio of the planetary gear set 30. The ring gearmember 44 rotates at the same speed as the output shaft 19. The ringgear member 44, and therefore the output shaft 19, rotates at a speeddetermined from the speed of the planet carrier assembly member 46, thespeed of the sun gear member 42, and the ring gear/sun gear tooth ratioof the planetary gear set 40. The numerical value of the reverse speedratio is determined utilizing the ring gear/sun gear tooth ratios of theplanetary gear sets 20, 30 and 40.

The extra reverse speed ratio (R′) is established with the engagement ofthe clutch 54 and the brake 59. The clutch 54 connects the sun gearmember 22 with the input shaft 17. The brake 59 connects the ring gearmember 34 with the transmission housing 60. The sun gear members 22 and42 rotate at the same speed as the input shaft 17. The planet carrierassembly member 26 rotates at the same speed as the planet carrierassembly member 36. The ring gear member 24 rotates at the same speed asthe sun gear member 32. The speed of the planet carrier assembly member26 is determined from the speed of the ring gear member 24, the speed ofthe sun gear member 22, and the ring gear/sun gear tooth ratio of theplanetary gear set 20. The ring gear member 34 and planet carrierassembly member 46 do not rotate. The planet carrier assembly member 36rotates at a speed determined from the speed of the sun gear member 32and the ring gear/sun gear tooth ratio of the planetary gear set 30. Thering gear member 44 rotates at the same speed as the output shaft 19.The ring gear member 44, and therefore the output shaft 19, rotates at aspeed determined from the speed of the sun gear member 42 and the ringgear/sun gear tooth ratio of the planetary gear set 40. The numericalvalue of the extra reverse speed ratio (R′) is determined utilizing thering gear/sun gear tooth ratios of the planetary gear sets 20, 30 and40.

The first forward speed ratio is established with the engagement of theclutch 54 and brake 58. The clutch connects the sun gear member 22 withthe input shaft 17. The brake 58 connects the planet carrier assemblymember 36 with the transmission housing 60. The sun gear members 22 and42 rotate at the same speed as the input shaft 17. The planet carrierassembly members 26, 36 do not rotate. The ring gear member 24 rotatesat the same speed as the sun gear member 32. The ring gear member 24rotates at a speed determined from the speed of the sun gear member 22and the ring gear/sun gear tooth ratio of the planetary gear set 20. Thering gear member 34 rotates at the same speed as the planet carrierassembly member 46. The ring gear member 34 rotates at a speeddetermined from the speed of the sun gear member 32 and the ringgear/sun gear tooth ratio of the planetary gear set 30. The ring gearmember 44 rotates at the same speed as the output shaft 19. The ringgear member 44, and therefore the output shaft 19, rotates at a speeddetermined from the speed of the planet carrier assembly member 46, thespeed of the sun gear member 42, and the ring gear/sun gear tooth ratioof the planetary gear set 40. The numerical value of the first forwardspeed ratio is determined utilizing the ring gear/sun gear tooth ratiosof the planetary gear sets 20, 30 and 40.

The second forward speed ratio is established with the engagement of theclutch 50 and the brake 59. The clutch 50 connects the ring gear member24 with the input shaft 17. The brake 59 connects the ring gear member34 with the transmission housing 60. The ring gear member 24 and sungear member 32 rotate at the same speed as the input shaft 17. Theplanet carrier assembly member 26 rotates at the same speed as theplanet carrier assembly member 36. The sun gear member 22 rotates at thesame speed as the sun gear member 42. The speed of the planet carrierassembly member 26 is determined from the speed of the ring gear member24, the speed of the sun gear member 22, and the ring gear/sun geartooth ratio of the planetary gear set 20. The ring gear member 34 andplanet carrier assembly member 46 do not rotate. The speed of the planetcarrier assembly member 36 is determined from the speed of the sun gearmember 32 and the ring gear/sun gear tooth ratio of the planetary gearset 30. The ring gear member 44 rotates at the same speed as the outputshaft 19. The ring gear member 44, and therefore the output shaft 19,rotates at a speed determined from the speed of the sun gear member 42and the ring gear/sun gear tooth ratio of the planetary gear set 40. Thenumerical value of the second forward speed ratio is determinedutilizing the ring gear/sun gear tooth ratios of the planetary gear sets20, 30 and 40.

The third forward speed ratio is established with the engagement of theclutch 56 and the brake 58. The clutch 56 connects the planet carrierassembly member 46 with the input shaft 17. The brake 58 connects theplanet carrier assembly member 36 with the transmission housing 60. Theplanet carrier assembly members 26, 36 do not rotate. The ring gearmember 24 rotates at the same speed as the sun gear member 32. The sungear member 22 rotates at the same speed as the sun gear member 42. Thespeed of the ring gear member 24 is determined from the speed of the sungear member 22 and the ring gear/sun gear tooth ratio of the planetarygear set 20. The ring gear member 34 and planet carrier assembly member46 rotate at the same speed as the input shaft 17. The speed of the sungear member 32 is determined from the speed of the ring gear member 34and the ring gear/sun gear tooth ratio of the planetary gear set 30. Thering gear member 44 rotates at the same speed as the output shaft 19.The ring gear member 44, and therefore the output shaft 19, rotates at aspeed determined from the speed of the planet carrier assembly member46, the speed of the sun gear member 42, and the ring gear/sun geartooth ratio of the planetary gear set 40. The numerical value of thethird forward speed ratio is determined utilizing the ring gear/sun geartooth ratios of the planetary gear sets 20, 30 and 40.

The fourth forward speed ratio is established with the engagement of theclutch 54 and the brake 57. The clutch 54 connects the sun gear member22 with the input shaft 17. The brake 57 connects the ring gear member24 with the transmission housing 60. The ring gear member 24 and sungear member 32 do not rotate. The planet carrier assembly member 26rotates at the same speed as the planet carrier assembly member 36. Thesun gear members 22, 42 rotate at the same speed as the input shaft 17.The speed of the planet carrier assembly member 26 is determined fromthe speed of the sun gear member 22 and the ring gear/sun gear toothratio of the planetary gear set 20. The ring gear member 34 rotates atthe same speed as the planet carrier assembly member 46. The ring gearmember 34 rotates at a speed determined from the speed of the planetcarrier assembly member 36 and the ring gear/sun gear tooth ratio of theplanetary gear set 30. The ring gear member 44 rotates at the same speedas the output shaft 19. The ring gear member 44, and therefore theoutput shaft 19, rotates at speed determined from the speed of theplanet carrier assembly member 46, the speed of the sun gear member 42,and the ring gear/sun gear tooth ratio of the planetary gear set 40. Thenumerical value of the fourth forward speed ratio is determinedutilizing the ring gear/sun gear tooth ratios of the planetary gear sets20, 30 and 40.

The fifth forward speed ratio is established with the engagement of theclutch 52 and the brake 59. The clutch 52 connects the planet carrierassembly member 26 with the input shaft 17. The brake 59 connects thering gear member 34 with the transmission housing 60. The ring gearmember 24 rotates at the same speed as the sun gear member 32. Theplanet carrier assembly members 26, 36 rotate at the same speed as theinput shaft 17. The sun gear member 22 rotates at the same speed as thesun gear member 42. The speed of the ring gear member 24 is determinedfrom the speed of the planet carrier assembly member 26, the speed ofthe sun gear member 22, and the ring gear/sun gear tooth ratio of theplanetary gear set 20. The ring gear member 34 and planet carrierassembly member 46 do not rotate. The speed of the sun gear member 32 isdetermined from the speed of the planet carrier assembly member 36 andthe ring gear/sun gear tooth ratio of the planetary gear set 30. Thering gear member 44 rotates at the same speed as the output shaft 19.The ring gear member 44, and therefore the output shaft 19, rotates at aspeed determined from the speed of the sun gear member 42 and the ringgear/sun gear tooth ratio of the planetary gear set 40. The numericalvalue of the fifth forward speed ratio is determined utilizing the ringgear/sun gear tooth ratios of the planetary gear sets 20, 30 and 40.

The sixth forward speed ratio is established with the engagement of theclutch 56 and the brake 57. The clutch 56 connects the planet carrierassembly member 46 with the input shaft 17. The brake 57 connects thering gear member 24 with the transmission housing 60. The ring gearmember 24 and sun gear member 32 do not rotate. The planet carrierassembly member 26 rotates at the same speed as the planet carrierassembly member 36. The sun gear member 22 rotates at the same speed asthe sun gear member 42. The speed of the planet carrier assembly member26 is determined from the speed of the sun gear member 22 and the ringgear/sun gear tooth ratio of the planetary gear set 20. The ring gearmember 34 and planet carrier assembly member 46 rotate at the same speedas the input shaft 17. The speed of the planet carrier assembly member36 is determined from the speed of the ring gear member 34 and the ringgear/sun gear tooth ratio of the planetary gear set 30. The ring gearmember 44 rotates at the same speed as the output shaft 19. The speed ofthe ring gear member 44, and therefore the output shaft 19, isdetermined from the speed of the planet carrier assembly member 46, thespeed of the sun gear member 42 and the ring gear/sun gear tooth ratioof the planetary gear set 40. The numerical value of the sixth forwardspeed ratio is determined utilizing the ring gear/sun gear tooth ratiosof the planetary gear sets 20, 30 and 40.

The seventh forward speed ratio is established with the engagement ofthe clutches 52 and 56. In this configuration, the input shaft 17 isdirectly connected to the output shaft 19. The numerical value of theseventh forward speed ratio is 1.

The eighth forward speed ratio is established with the engagement of theclutch 52 and the brake 57. The clutch 52 connects the planet carrierassembly member 26 with the input shaft 17. The brake 57 connects thering gear member 24 with the transmission housing 60. The ring gearmember 24 and sun gear member 32 do not rotate. The planet carrierassembly members 26, 36 rotate at the same speed as the input shaft 17.The speed of the sun gear member 22 is determined from the speed of theplanet carrier assembly member 26 and the ring gear/sun gear tooth ratioof the planetary gear set 20. The ring gear member 34 rotates at thesame speed as the planet carrier assembly member 46. The speed of thering gear member 34 is determined from the speed of the planet carrierassembly member 36 and the ring gear/sun gear tooth ratio of theplanetary gear set 30. The ring gear member 44 rotates at the same speedas the output shaft 19. The ring gear member 44, and therefore theoutput shaft 19, rotates at a speed determined from the speed of theplanet carrier assembly member 46, the speed of the sun gear member 42,and the ring gear/sun gear tooth ratio of the planetary gear set 40. Thenumerical value of the eighth forward speed ratio is determinedutilizing the ring gear/sun gear tooth ratios of the planetary gear sets20, 30 and 40.

As set forth above, the engagement schedule for the torque-transmittingmechanisms is shown in the truth table of FIG. 1 b. This truth tablealso provides an example of speed ratios that are available utilizingthe ring gear/sun gear tooth ratios given by way of example in FIG. 1 b.The N_(R1)/N_(S1) value is the tooth ratio of the planetary gear set 20;the N_(R2)/N_(S2) value is the tooth ratio of the planetary gear set 30;and the N_(R3)/N_(S3) value is the tooth ratio of the planetary gear set40. Also, the chart of FIG. 1 b describes the ratio steps that areattained utilizing the sample of tooth ratios given. For example, thestep ratio between the first and second forward speed ratios is 1.52,while the step ratio between the reverse and first forward ratio is−0.67.

FIG. 2 a shows a powertrain 110 having a conventional engine 12, aplanetary transmission 114, and a conventional final drive mechanism 16.

The planetary transmission 114 includes an input shaft 17 continuouslyconnected with the engine 12, a planetary gear arrangement 118, and anoutput shaft 19 continuously connected with the final drive mechanism16. The planetary gear arrangement 118 includes three planetary gearsets 120, 130 and 140.

The planetary gear set 120 includes a sun gear member 122, a ring gearmember 124, and a planet carrier assembly 126. The planet carrierassembly 126 includes a plurality of pinion gears 127 rotatably mountedon a carrier member 129 and disposed in meshing relationship with boththe sun gear member 122 and the ring gear member 124.

The planetary gear set 130 includes a sun gear member 132, a ring gearmember 134, and a planet carrier assembly member 136. The planet carrierassembly member 136 includes a plurality of pinion gears 137 rotatablymounted on a carrier member 139 and disposed in meshing relationshipwith both the sun gear member 132 and the ring gear member 134.

The planetary gear set 140 includes a sun gear member 142, a ring gearmember 144, and a planet carrier assembly member 146. The planet carrierassembly member 146 includes a plurality of pinion gears 147 rotatablymounted on a carrier member 149 and disposed in meshing relationshipwith both the sun gear member 142 and the ring gear member 144.

The planetary gear arrangement 118 also includes seventorque-transmitting mechanisms 150, 152, 154, 156, 157, 158 and 159. Thetorque-transmitting mechanisms 150, 152 and 154 are rotating-typetorque-transmitting mechanisms, commonly termed clutches. Thetorque-transmitting mechanisms 156, 157, 158 and 159 are stationary-typetorque transmitting mechanisms, commonly termed brakes or reactionclutches.

The input shaft 17 is not continuously connected with any planetary gearmember. The output shaft 19 is continuously connected with the sun gearmember 142. The ring gear member 124 is continuously connected with thering gear member 144 through the interconnecting member 170. The planetcarrier assembly member 126 is continuously connected with the planetcarrier assembly member 136 through the interconnecting member 172. Thering gear member 134 is continuously connected with the planet carrierassembly member 146 through the interconnecting member 174. The sun gearmember 122 is continuously connected with the sun gear member 132through the interconnecting member 176.

The sun gear member 122 is selectively connectable with the input shaft17 through the clutch 150. The planet carrier assembly member 136 isselectively connectable with the input shaft 17 through the clutch 152.The ring gear member 134 is selectively connectable with the input shaft17 through the clutch 154. The sun gear member 122 is selectivelyconnectable with the transmission housing 160 through the brake 156. Theplanet carrier assembly member 126 is selectively connectable with thetransmission housing 160 through the brake 157. The ring gear member 144is selectively connectable with the transmission housing 160 through thebrake 158. The planet carrier assembly member 146 is selectivelyconnectable with the transmission housing 160 through the brake 159.

The truth table of FIG. 2b describes the engagement sequence utilized toprovide eight forward speed ratios and one reverse speed ratio in theplanetary gear arrangement 118 shown in FIG. 2 a, as well as an extraeighth forward speed ratio.

The truth tables given in FIGS. 2 b, 3 b, 4 b, 5 b, 6 b and 7 b show theengagement sequences for the torque-transmitting mechanisms to provideat least eight forward speed ratios and at least one reverse ratio. Asshown and described above for the configuration in FIG. 1 a, thoseskilled in the art will understand from the respective truth tables howthe speed ratios are established through the planetary gear setsidentified in the written description.

As set forth above, the truth table of FIG. 2 b describes the engagementsequence of the torque-transmitting mechanisms utilized to provide thereverse drive ratio and eight forward speed ratios, as well as the extraeighth forward speed ratio. The truth table also provides an example ofthe ratios that can be attained with the family members shown in FIG. 2a utilizing the sample tooth ratios given in FIG. 2 b. The N_(R1)/N_(S1)value is the tooth ratio of the planetary gear set 120; theN_(R2)/N_(S2) value is the tooth ratio of the planetary gear set 130;and the N_(R3)/N_(S3) value is the tooth ratio of the planetary gear set140. Also shown in FIG. 2 b are the ratio steps between single stepratios in the forward direction as well as the reverse to first stepratio. For example, the first to second step ratio is 1.56.

Turning to FIG. 3 a, a powertrain 210 includes the engine 12, aplanetary transmission 214, and a final drive mechanism 16. Theplanetary transmission 214 includes an input shaft 17 continuouslyconnected with the engine 12, a planetary gear arrangement 218, and anoutput shaft 19 continuously connected with the final drive mechanism16. The planetary gear arrangement 218 includes three planetary gearsets 220, 230 and 240.

The planetary gear set 220 includes a sun gear member 222, a ring gearmember 224, and a planet carrier assembly 226. The planet carrierassembly 226 includes a plurality of pinion gears 227 rotatably mountedon a carrier member 229 and disposed in meshing relationship with boththe sun gear member 222 and the ring gear member 224.

The planetary gear set 230 includes a sun gear member 232, a ring gearmember 234, and a planet carrier assembly member 236. The planet carrierassembly member 236 includes a plurality of pinion gears 237 rotatablymounted on a carrier member 239 and disposed in meshing relationshipwith both the sun gear member 232 and the ring gear member 234.

The planetary gear set 240 includes a sun gear member 242, a ring gearmember 244, and a planet carrier assembly member 246. The planet carrierassembly member 246 includes a plurality of pinion gears 247, 248rotatably mounted on a carrier member 249, wherein the pinion gears 247are disposed in meshing relationship with the sun gear member 242 andthe pinion gears 248 are disposed in meshing relationship with the ringgear member 244 and with the pinion gears 247.

The planetary gear arrangement 218 also includes seventorque-transmitting mechanisms 250, 252, 254, 256, 257, 258 and 259. Thetorque-transmitting mechanisms 250, 252, and 254 are rotating typetorque-transmitting mechanisms, commonly termed clutches. Thetorque-transmitting mechanisms 256, 257, 258 and 259 are stationary-typetorque transmitting mechanism, commonly termed brake or reaction clutch.

The input shaft 17 is not continuously connected with any planetary gearmember. The output shaft 19 is continuously connected with the ring gearmember 224. The planet carrier assembly member 226 is continuousconnected with the ring gear member 244 through the interconnectingmember 270. The sun gear member 222 is continuously connected with theplanet carrier assembly member 236 through the interconnecting member272. The ring gear member 224 is continuously connected with the sungear member 232 through the interconnecting member 274. The ring gearmember 234 is continuously connected with the planet carrier assemblymember 246 through the interconnecting member 276.

The ring gear member 244 is selectively connectable with the input shaft17 through the clutch 250. The planet carrier assembly member 246 isselectively connectable with the input shaft 17 through the clutch 252.The sun gear member 242 is selectively connectable with the input shaft17 through the clutch 254. The planet carrier assembly member 236 isselectively connectable with the transmission housing 260 through thebrake 256. The ring gear member 244 is selectively connectable with thetransmission housing 260 through the brake 257. The planet carrierassembly member 246 is selectively connectable with the transmissionhousing 260 through the brake 258. The sun gear member 242 is selectiveconnectable with the transmission housing 260 through the brake 259.

As shown in the truth table in FIG. 3 b, the torque-transmittingmechanisms are engaged in combinations of two to establish eight forwardspeed ratios and two reverse speed ratios.

As previously set forth, the truth table of FIG. 3 b describes thecombinations of engagements utilized for the forward and reverse speedratios. The truth table also provides an example of speed ratios thatare available with the family member described above. These examples ofspeed ratios are determined utilizing the tooth ratios given in FIG. 3b. The N_(R1)/N_(S1) value is the tooth ratio of the planetary gear set220; the N_(R2)/N_(S2) value is the tooth ratio of the planetary gearset 230; and the N_(R3)/N_(S3) value is the tooth ratio of the planetarygear set 240. Also depicted in FIG. 3 b is a chart representing theratio steps between adjacent forward speed ratios and between the firstand reverse speed ratio. For example, the first to second ratiointerchange has a step of 2.31.

A powertrain 310, shown in FIG. 4 a, includes the engine 12, a planetarytransmission 314, and the final drive mechanism 16. The planetarytransmission 314 includes an input shaft 17 continuously connected withthe engine 12, a planetary gear arrangement 318, and an output shaft 19continuously connected with the final drive mechanism 16. The planetarygear arrangement 318 includes three planetary gear sets 320, 330 and340.

The planetary gear set 320 includes a sun gear member 322, a ring gearmember 324, and a planet carrier assembly member 326. The planet carrierassembly member 326 includes a plurality of pinion gears 327 rotatablymounted on a carrier member 329 and disposed in meshing relationshipwith both the sun gear member 322 and the ring gear member 324.

The planetary gear set 330 includes a sun gear member 332, a ring gearmember 334, and a planet carrier assembly member 336. The planet carrierassembly member 336 includes a plurality of pinion gears 337 rotatablymounted on a carrier member 339 and disposed in meshing relationshipwith both the sun gear member 332 and the ring gear member 334.

The planetary gear set 340 includes a sun gear member 342, a ring gearmember 344, and a planet carrier assembly member 346. The planet carrierassembly member 346 includes a plurality of pinion gears 347 rotatablymounted on a carrier member 349 and disposed in meshing relationshipwith both the sun gear member 342 and the ring gear member 344.

The planetary gear arrangement 318 also includes seventorque-transmitting mechanisms 350, 352, 354, 356, 357, 358 and 359. Thetorque-transmitting mechanisms 350, 352 and 354 are rotating typetorque-transmitting mechanisms, commonly termed clutches. Thetorque-transmitting mechanisms 356, 357, 358 and 359 are stationary typetorque transfer devices commonly termed brakes or reaction clutches.

The input shaft 17 is not continuously connected with any planetary gearmember. The output shaft 19 is continuously connected with the ring gearmember 344. The planet carrier assembly member 326 is continuouslyconnected with the planet carrier assembly member 336 through theinterconnecting member 370. The ring gear member 324 is continuouslyconnected with the sun gear member 332 through the interconnectingmember 372. The sun gear member 322 is continuously connected with thesun gear member 342 through the interconnecting member 374. The ringgear member 334 is continuously connected with the planet carrierassembly member 346 through the interconnecting member 376.

The ring gear member 324 is selectively connectable with the input shaft17 through the clutch 350. The planet carrier assembly member 326 isselectively connectable with the input shaft 17 through the clutch 352.The sun gear member 322 is selectively connectable with the input shaft17 through the clutch 354. The ring gear member 324 is selectivelyconnectable with the transmission housing 360 through the clutch 356.The planet carrier assembly member 336 is selectively connectable withthe transmission housing 360 through the brake 357. The sun gear member322 is selectively connectable with the transmission housing 360 throughthe brake 358. The ring gear member 334 is selectively connectable withthe transmission housing 360 through the brake 359.

The truth table shown in FIG. 4 b describes the engagement combinationand the engagement sequence necessary to provide two reverse driveratios and eight forward speed ratios. A sample of the numerical valuesfor the ratios is also provided in the truth table of FIG. 4 b. Thesevalues are determined utilizing the ring gear/sun gear tooth ratios alsogiven in FIG. 4 b. The N_(R1)/N_(S1) value is the tooth ratio for theplanetary gear set 320; the N_(R2)/N_(S2) value is the tooth ratio forthe planetary gear set 330; and the N_(R3)/N_(S3) value is the toothratio for the planetary gear set 340. Also given in FIG. 4 b is a chartdescribing the step ratios between the adjacent forward speed ratios andthe reverse to first forward speed ratio. For example, the first tosecond forward speed ratio step is 2.34.

A powertrain 410, shown in FIG. 5 a, includes the engine 12, a planetarytransmission 414 and the final drive mechanism 16. The planetarytransmission 414 includes a planetary gear arrangement 418, input shaft17 and output shaft 19. The planetary gear arrangement 418 includesthree simple planetary gear sets 420, 430 and 440.

The planetary gear set 420 includes a sun gear member 422, a ring gearmember 424, and a planet carrier assembly 426. The planet carrierassembly 426 includes a plurality of pinion gears 427 rotatably mountedon a carrier member 429 and disposed in meshing relationship with boththe sun gear member 422 and the ring gear member 424.

The planetary gear set 430 includes a sun gear member 432, a ring gearmember 434, and a planet carrier assembly member 436. The planet carrierassembly member 436 includes a plurality of pinion gears 437 rotatablymounted on a carrier member 439 and disposed in meshing relationshipwith both the ring gear member 434 and the sun gear member 432.

The planetary gear set 440 includes a sun gear member 442, a ring gearmember 444, and a planet carrier assembly member 446. The planet carrierassembly member 446 includes a plurality of pinion gears 447 rotatablymounted on a carrier member 449 and disposed in meshing relationshipwith both the sun gear member 442 and the ring gear member 444.

The planetary gear arrangement 418 also includes seventorque-transmitting mechanisms 450, 452, 454, 456, 457, 458 and 459. Thetorque-transmitting mechanisms 450, 452, 454 and 456 are rotating typetorque-transmitting mechanisms, commonly termed clutches. Thetorque-transmitting mechanisms 457, 458 and 459 are stationary-typetorque transmitting mechanisms, commonly termed brakes or reactionclutches.

The input shaft 17 is not continuously connected with any planetary gearmember. The output shaft 19 is continuously connected with the planetcarrier assembly member 426. The ring gear member 424 is continuouslyconnected with the planet carrier assembly member 446 through theinterconnecting member 470. The ring gear member 434 is continuouslyconnected with the planet carrier assembly member 426 through theinterconnecting member 472. The sun gear member 422 is continuouslyconnected with the planet carrier assembly member 436 through theinterconnecting member 474. The sun gear member 432 is continuouslyconnected with the ring gear member 444 through the interconnectingmember 444.

The planet carrier assembly member 436 is selectively connectable withthe input shaft 17 through the clutch 450. The planet carrier assemblymember 446 is selectively connectable with the input shaft 17 throughthe clutch 452. The sun gear member 432 is selectively connectable withthe input shaft 17 through the clutch 454. The sun gear member 442 isselectively connectable with the input shaft 17 through the clutch 456.The sun gear member 422 is selectively connectable with the transmissionhousing 460 through the brake 457. The ring gear member 424 isselectively connectable with the transmission housing 460 through thebrake 458. The sun gear member 442 is selectively connectable with thetransmission housing 460 through the brake 459.

The truth table shown in FIG. 5b describes the engagement combinationand sequence of the torque-transmitting mechanisms 450, 452, 454, 456,457, 458 and 459 that are employed to provide the forward and reversedrive ratios.

Also given in the truth table of FIG. 5 b is a set of numerical valuesthat are attainable with the present invention utilizing the ringgear/sun gear tooth ratios shown. The N_(R1)/N_(S1) value is the toothratio of the planetary gear set 420; the N_(R2)/N_(S2) value is thetooth ratio of the planetary gear set 430; and the N_(R3)/N_(S3) valueis the tooth ratio of the planetary gear set 440.

FIG. 5 b also provides a chart of the ratio steps between adjacentforward ratios and between the reverse and first forward ratio. Forexample, the ratio step between the first and second forward ratios is2.29.

A powertrain 510, shown in FIG. 6 a, includes an engine 12, a planetarygear transmission 514 and the final drive mechanism 16. The planetarytransmission 514 includes the input shaft 17, a planetary geararrangement 518 and the output shaft 19. The planetary gear arrangement518 includes three planetary gear sets 520, 530 and 540.

The planetary gear set 520 includes a sun gear member 522, a ring gearmember 524, and a planet carrier assembly 526. The planet carrierassembly 526 includes a plurality of pinion gears 527 rotatably mountedon a carrier member 529 and disposed in meshing relationship with boththe sun gear member 522 and the ring gear member 524.

The planetary gear set 530 includes a sun gear member 532, a ring gearmember 534, and a planet carrier assembly member 536. The planet carrierassembly member 536 includes a plurality of pinion gears 537 rotatablymounted on a carrier member 539 and disposed in meshing relationshipwith both the sun gear member 532 and the ring gear member 534.

The planetary gear set 540 includes a sun gear member 542, a ring gearmember 544, and a planet carrier assembly member 546. The planet carrierassembly member 546 includes a plurality of pinion gears 547 rotatablymounted on a carrier member 549 and disposed in meshing relationshipwith both the sun gear member 542 and the ring gear member 544.

The planetary gear arrangement 518 also includes seventorque-transmitting mechanisms 550, 552, 554, 556, 557, 558 and 559. Thetorque-transmitting mechanisms 550, 552, 554 and 556 are rotating typetorque-transmitting mechanisms, commonly termed clutches. Thetorque-transmitting mechanisms 557, 558 and 559 are stationary-typetorque transmitting mechanisms, commonly termed brakes or reactionclutches.

The input shaft 17 is not continuously connected with any planetary gearmember. The output shaft 19 is continuously connected with the planetcarrier assembly member 526. The planet carrier assembly member 526 iscontinuously connected with the sun gear member 532 through theinterconnecting member 570. The ring gear member 524 is continuouslyconnected with the planet carrier assembly member 546 through theinterconnecting member 572. The sun gear member 522 is continuouslyconnected with the planet carrier assembly member 536 through theinterconnecting member 574. The ring gear member 534 is continuouslyconnected with the sun gear member 542 through the interconnectingmember 576.

The planet carrier assembly member 536 is selectively connectable withthe input shaft 17 through the clutch 550. The planet carrier assemblymember 546 is selectively connectable with the input shaft 17 throughthe clutch 552. The sun gear member 542 is selectively connectable withthe input shaft 17 through the clutch 554. The ring gear member 544 isselectively connectable with the input shaft 17 through the clutch 556.The sun gear member 522 is selectively connectable with the transmissionhousing 560 through the brake 557. The ring gear member 524 isselectively connectable with the transmission housing 560 through thebrake 558. The ring gear member 544 is selectively connectable with thetransmission housing 560 through the brake 559.

The truth table shown in FIG. 6b describes the engagement sequence andcombination of the torque-transmitting mechanisms to provide two reversespeed ratios and eight forward speed ratios. The chart of FIG. 6 bdescribes the ratio steps between adjacent forward speed ratios and theratio step between the reverse and first forward speed ratio.

The sample speed ratios given in the truth table are determinedutilizing the tooth ratio values also given in FIG. 6 b. TheN_(R1)/N_(S1) value is the tooth ratio of the planetary gear set 520;the N_(R2)/N_(S2) value is the tooth ratio of the planetary gear set530; and the N_(R3)/N_(S3) value is the tooth ratio of the planetarygear set 540.

A powertrain 610, shown in FIG. 7 a, has the engine 12, a planetarytransmission 614 and the final drive mechanism 16. The planetarytransmission 614 includes the input shaft 17, a planetary geararrangement 618 and the output shaft 19. The planetary gear arrangement618 includes three planetary gear sets 620, 630 and 640.

The planetary gear set 620 includes a sun gear member 622, a ring gearmember 624, and a planet carrier assembly 626. The planet carrierassembly 626 includes a plurality of pinion gears 627 rotatably mountedon a carrier member 629 and disposed in meshing relationship with boththe sun gear member 622 and the ring gear member 624.

The planetary gear set 630 includes a sun gear member 632, a ring gearmember 634, and a planet carrier assembly member 636. The planet carrierassembly member 636 includes a plurality of pinion gears 637 rotatablymounted on a carrier member 639 and disposed in meshing relationshipwith both the sun gear member 632 and the ring gear member 634.

The planetary gear set 640 includes a sun gear member 642, a ring gearmember 644, and a planet carrier assembly member 646. The planet carrierassembly member 646 includes a plurality of pinion gears 647 rotatablymounted on a carrier member 649 and disposed in meshing relationshipwith both the sun gear member 642 and the ring gear member 644.

The planetary gear arrangement 618 also includes seventorque-transmitting mechanisms 650, 652, 654, 656, 657, 658 and 659. Thetorque-transmitting mechanisms 650, 652 and 654 are rotating typetorque-transmitting mechanisms, commonly termed clutches. Thetorque-transmitting mechanisms 656, 657, 658 and 659 are stationary-typetorque transmitting mechanisms, commonly termed brakes or reactionclutches.

The input shaft 17 is not continuously connected with any planetary gearmember. The output shaft 19 is continuously connected with the planetcarrier assembly member 626. The ring gear member 624 is continuouslyconnected with the sun gear member 632 through the interconnectingmember 670. The planet carrier assembly member 626 is continuouslyconnected with the planet carrier assembly member 636 through theinterconnecting member 672. The ring gear member 634 is continuouslyconnected with the planet carrier assembly member 646 through theinterconnecting member 674. The sun gear member 622 is continuouslyconnected with the sun gear member 642 through the interconnectingmember 676.

The sun gear member 642 is selectively connectable with the input shaft17 through the clutch 650. The planet carrier assembly member 646 isselectively connectable with the input shaft 17 through the clutch 652.The ring gear member 644 is selectively connectable with the input shaft17 through the clutch 654. The ring gear member 624 is selectivelyconnectable with the transmission housing 660 through the brake 656. Thesun gear member 622 is selectively connectable with the transmissionhousing 660 through the brake 657. The ring gear member 634 isselectively connectable with the transmission housing 660 through thebrake 658. The ring gear member 644 is selectively connectable with thetransmission housing 660 through the brake 659.

The truth table shown in FIG. 7b describes the combination oftorque-transmitting mechanism engagements that will provide the reversedrive ratio and nine forward speed ratios, as well as the sequence ofthese engagements and interchanges.

The ratio values given are by way of example and are establishedutilizing the ring gear/sun gear tooth ratios given in FIG. 7 b. Forexample, the N_(R1)/N_(S1) value is the tooth ratio of the planetarygear set 620; the N_(R2)/N_(S2) value is the tooth ratio of theplanetary gear set 630; and the N_(R3)/N_(S3) value is the tooth ratioof the planetary gear set 640. The ratio steps between adjacent forwardratios and the reverse to first ratio are also given in FIG. 7 b.

While the best modes for carrying out the invention have been describedin detail, those familiar with the art to which this invention relateswill recognize various alternative designs and embodiments forpracticing the invention within the scope of the appended claims.

1. A multi-speed transmission comprising: an input shaft; an outputshaft; first, second and third planetary gear sets each having first,second and third members; said output shaft being continuouslyinterconnected with a member of said planetary gear sets, and said inputshaft not being continuously interconnected with any member of saidplanetary gear sets; a first interconnecting member continuouslyinterconnecting said first member of said first planetary gear set withsaid first member of said second planetary gear set; a secondinterconnecting member continuously interconnecting said second memberof said first planetary gear set with said second member of said secondplanetary gear set; a third interconnecting member continuouslyinterconnecting said third member of said first planetary gear set withsaid first member of said third planetary gear set; a fourthinterconnecting member continuously interconnecting said third member ofsaid second planetary gear set with said second member of said thirdplanetary gear set; a first torque-transmitting mechanism selectivelyinterconnecting a member of said first planetary gear set with saidinput shaft; a second torque-transmitting mechanism selectivelyinterconnecting a member of said second planetary gear set with saidinput shaft; a third torque-transmitting mechanism selectivelyinterconnecting a member of said first or third planetary gear set withsaid input shaft; a fourth torque-transmitting mechanism selectivelyinterconnecting a member of said first planetary gear set with astationary member; a fifth torque-transmitting mechanism selectivelyinterconnecting a member of said second planetary gear set with saidstationary member; a sixth torque-transmitting mechanism selectivelyinterconnecting a member of said first or third planetary gear set withsaid stationary member; and a seventh torque-transmitting mechanismselectively interconnecting a member of said first, second or thirdplanetary gear set with another member of said first, second or thirdplanetary gear set, or with said stationary member; saidtorque-transmitting mechanisms being engaged in combinations of two toestablish at least eight forward speed ratios and at least one reversespeed ratio between said input shaft and said output shaft.
 2. Thetransmission defined in claim 1, wherein said first, second and thirdtorque-transmitting mechanisms comprise clutches, and said fourth,fifth, sixth and seventh torque-transmitting mechanisms comprise brakes.3. The transmission defined in claim 1, wherein said first, second,third and seventh torque-transmitting mechanisms comprise clutches, andsaid fourth, fifth, and sixth torque-transmitting mechanisms comprisebrakes.
 4. The transmission defined in claim 1, wherein planet carrierassembly members of each of said planetary gear sets are single-pinioncarriers.
 5. The transmission defined in claim 1, wherein at least oneplanet carrier assembly member of said planetary gear sets is adouble-pinion carrier.
 6. The transmission defined in claim 1, whereintwo planet carrier assembly members of said planetary gear sets aredouble-pinion carriers.
 7. A multi-speed transmission comprising: aninput shaft; an output shaft; a planetary gear arrangement having first,second and third planetary gear sets, each planetary gear set havingfirst, second and third members; said output shaft being continuouslyinterconnected with a member of said planetary gear sets, and said inputshaft not being continuously interconnected with any member of saidplanetary gear sets; a first interconnecting member continuouslyinterconnecting said first member of said first planetary gear set withsaid first member of said second planetary gear set; a secondinterconnecting member continuously interconnecting said second memberof said first planetary gear set with said second member of said secondplanetary gear set; a third interconnecting member continuouslyinterconnecting said third member of said first planetary gear set withsaid first member of said third planetary gear set; a fourthinterconnecting member continuously interconnecting said third member ofsaid second planetary gear set with said second member of said thirdplanetary gear set; and seven torque-transmitting mechanisms forselectively interconnecting said members of said planetary gear setswith said input shaft, with a stationary member or with other members ofsaid planetary gear sets, said seven torque-transmitting mechanismsbeing engaged in combinations of two to establish at least eight forwardspeed ratios and at least one reverse speed ratio between said inputshaft and said output shaft.
 8. The transmission defined in claim 7,wherein a first of said seven torque-transmitting mechanisms is operablefor selectively interconnecting a member of said first planetary gearset with said input shaft.
 9. The transmission defined in claim 7,wherein a second of said seven torque-transmitting mechanisms isoperable for selectively interconnecting a member of said secondplanetary gear set with said input shaft.
 10. The transmission definedin claim 7, wherein a third of said seven torque-transmitting mechanismsis selectively operable for interconnecting a member of said first orthird planetary gear set with said input shaft.
 11. The transmissiondefined in claim 7, wherein a fourth of said seven torque-transmittingmechanisms is selectively operable for interconnecting a member of saidfirst planetary gear set with said stationary member.
 12. Thetransmission defined in claim 7, wherein a fifth of said seventorque-transmitting mechanisms is selectively operable forinterconnecting a member of said second planetary gear set with saidstationary member.
 13. The transmission defined in claim 7, wherein asixth of said seven torque-transmitting mechanisms selectivelyinterconnects a member of said first or third planetary gear set withsaid stationary member.
 14. The transmission defined in claim 7, whereina seventh of said seven torque-transmitting mechanisms selectivelyinterconnects a member of said first, second or third planetary gear setwith another member of said first, second or third planetary gear set,or with said stationary member.
 15. The transmission defined in claim 7,wherein planet carrier assembly members of each of said planetary gearsets are single-pinion carriers.
 16. The transmission defined in claim7, wherein at least one planet carrier assembly member of said planetarygear sets is a double-pinion carrier.